Manufacturing method for compound semiconductor device

ABSTRACT

It is the object of the present invention to provide a manufacturing method for a compound semiconductor device capable of removing remaining organic substances without deteriorating a characteristic of the compound semiconductor device, wherein a surface of an i-type AlGaAs schottky layer  105  is cleaned in a state where light is blocked using either one of ozone (O 3 ) water whose ozone concentration is 13 mg/L or less and hydrogen (H 2 ) water whose hydrogen ion concentration (pH) is from 6 to 8 inclusive, or using both of the ozone water and the hydrogen water after a schottky electrode  111  made of Ti/Al/Ti is evaporated onto the exposed i-type AlGaAs schottky layer  105  and a lift-off is performed using a remover.

BACKGROUND OF THE INVENTION

(1) Field of the Invention

The present invention relates to a manufacturing method for a compound semiconductor device, in particular to a manufacturing method for a compound semiconductor device, the method including a surface-cleaning process after a resist pattern is removed.

(2) Description of the Related Art

Generally speaking, in a lithography process of the manufacturing process for the semiconductor device, a resist pattern is formed on a semiconductor layer, the semiconductor layer is etched using the resist pattern, and the resist pattern is removed using a remover and the like.

In the lithography process, if organic substances such as resist still remain on the semiconductor layer after the resist pattern is removed, the remaining substances result in a film removal and the like. It is possible to cause a problem on credibility. Accordingly, in order to remove the remaining organic substances, an O₂ plasma ashing is performed on the semiconductor layer after the resist is removed (e.g. refer to Ralph E. Williams. “Gallium Arsenide Processing Techniques” (United States), ARTECH HOUSE, INC., 1984). In addition, according to the technology disclosed in Japanese Laid-Open Patent Publication application No. 2001-185520, the remaining organic substances made of Si on the semiconductor layer are removed by combining ozone gas, ozone water and hydrogen water.

By the way, in the case where the semiconductor layer is a compound semiconductor layer made of GaAs and the like instead of Si, a desired device characteristic of the compound semiconductor device cannot be obtained when the remaining organic substances are removed by the O₂ plasma ashing in a lithography process of the compound semiconductor device having such compound semiconductor layer. That is, the compound semiconductor layer is damaged when the O₂ plasma ashing is performed on the semiconductor layer in a state where the compound semiconductor layer is exposed after the removal of the resist pattern.

Here, the removal of the organic substances remained on the compound semiconductor layer not by the O₂ plasma ashing but by ozone gas, ozone water and hydrogen water had not been practiced under a consideration of the strong oxidization capability of the ozone gas, the ozone water and the hydrogen water.

SUMMARY OF THE INVENTION

Considering the problem mentioned above, it is an object of the present invention to provide a manufacturing method for a compound semiconductor device capable of removing remaining organic substances without deteriorating a characteristic of the compound semiconductor device.

In order to achieve the object, the manufacturing method of the compound semiconductor device of the present invention comprises a patterning process of forming a resist pattern on a compound semiconductor layer; and a removing process of removing said resist patter and cleaning a surface of the compound semiconductor layer using at least one of ozone (O₃) water and hydrogen (H₂) water. In here, a concentration of the ozone water may be 13 mg/L or less. Also, the compound semiconductor layer may have a layer made of GaAs, AlGaAs, InGaAs, InGaP, or InP. Also, the compound semiconductor layer surface to be cleaned may be made of GaAs, AlGaAs, InGaAs, InGaP, or InP.

Consequently, the remaining organic substances can be removed without damaging the compound semiconductor layer so that the manufacturing method for the compound semiconductor device capable of removing the remaining organic substances without deteriorating the characteristic of the compound semiconductor device can be realized.

In here, the cleaning of the compound semiconductor layer surface in the removing process may be performed in a state where light is blocked.

As the result, the compound semiconductor layer to be cleaned is not etched by a buttery effect so that the manufacturing method for the compound semiconductor device of further preventing a deterioration of the characteristic of the compound semiconductor device can be realized.

Further, in the removing process, the ozone water and the hydrogen water may be used for the cleaning.

Consequently, many of the remaining organic substances can be removed by oxidation of ozone water and deoxidization of the hydrogen water. Further, the remaining fluid on the surface of the compound semiconductor layer can be removed by rinsing with the hydrogen water. Therefore, the manufacturing method for the compound semiconductor device capable of further cleaning the surface of the compound semiconductor layer can be realized.

As is clear from the explanation, according to the manufacturing method for the compound semiconductor device of the present invention, the remaining organic substances can be removed without deteriorating the characteristic of the compound semiconductor device.

Accordingly, the present invention makes it possible to provide the manufacturing method for the compound semiconductor device capable of removing the remaining organic substances without deteriorating the characteristic of the compound semiconductor device. The practical value of the present invention is therefore very high.

As further information about technical background to this application, the disclosure of Japanese Patent Application No. 2004-023238 filed on Jan. 30, 2004 including specification, drawings and claims is incorporated herein by reference in its entirety.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other objects, advantages and features of the invention will become apparent from the following description thereof taken in conjunction with the accompanying drawings that illustrate a specific embodiment of the invention. In the Drawings:

FIGS. 1A to 1G are cross-section diagrams of a field effect transistor (hereafter referred to as FET) for explaining a lithography process in the present embodiment of the present invention.

FIG. 2 is a diagram indicating an I_(ds)-V_(gs) characteristic of the FET manufactured through the lithography process of the present embodiment.

FIG. 3 is a diagram indicating a result of comparing the number of particles of the FET manufactured through the lithography process in the present embodiment with the number of particles of the FET manufactured through the conventional lithography process.

FIG. 4 is a diagram indicating an I_(ds) variation of the FET in the case where an ozone concentration of ozone water is changed in the lithography process of the present embodiment.

DESCRIPTION OF THE PREFERRED EMBODIMENT(S)

Hereafter, the manufacturing method for the compound semiconductor device according to the present embodiment of the present invention is explained with reference to diagrams.

FIGS. 1A to IG are cross-section diagrams of a FET for explaining a lithography process in the manufacturing process of the FET in the present embodiment.

Firstly, as shown in FIG. 1A, on a semi-insulate GaAs substrate 102, an epitaxial layer 101 is generated by epitaxially growing, in sequence, an i-type InGaAs channel layer 103, a n-type AlGaAs electron supply layer 104, an i-type AlGaAs schottky layer 105, and a n-type GaAs ohmic contact layer 106.

Next, as shown in FIG. 1B, a SiO₂ film 107 with a thickness of, for example, 300 nm is formed on the epitaxial layer 101 by the plasma CVD method.

Then, as shown in FIG. 1C, after a resist pattern 108 for forming an ohmic electrode 109 is formed, a predetermined region of the SiO₂ film 107 is etched with fluorine using the resist pattern 108 so as to expose the n-type ohmic contact layer 106.

Following that, as shown in FIG. 1D, the ohmic electrode 109 made of AuGe/Ni/Au system is evaporated on the exposed n-type GaAs ohmic contact layer 106 and a lift-off is performed using a remover.

Next, as shown in FIG. 1E, after a resist pattern 110 for forming a schottky electrode 111 is formed, the predetermined region of the SiO₂ film 107 is etched with fluorine using the resist pattern 110.

Then, as shown in FIG. 1F, the epitaxial layer 101 is recess-etched and the i-type AlGaAs schottky layer 105 is exposed.

Finally, as shown in FIG. 1G, the schottky electrode 111 made of Ti/Al/Ti system is evaporated on the exposed i-type AlGaAs schottky layer 105 and a lift-off is performed using the remover. Further, the surface of the epitaxial layer 101 is cleaned by dipping with ozone water (O₃) whose ozone concentration is 13 mg/L or less, for example, 5 mg/L at a normal temperature for about 90 sec, and the remaining organic substances are removed. Here, the cleaning is performed in a state where light is blocked in order to shade the epitaxial layer 101. In here, a pH of the ozone water is preferred to be from 6 to 8 inclusive. Also, not the ozone water but the hydrogen water whose concentration is from 6 to 8 inclusive, or the hydrogen water and the ozone water, for example, the hydrogen water whose hydrogen ion concentration is 7, may be used for cleaning the surface of the epitaxial layer 101. When the surface of the epitaxial layer 101 is cleaned with the hydrogen water and the ozone water, a cleaning with the ozone water or the hydrogen water is performed after the cleaning with the hydrogen water or the ozone water. Further, while it is explained that the dipping process with the ozone water cleans the surface of the epitaxial layer 101, a similar effect is obtained in a spin process that spins the GaAs substrate and discharges ozone water from a nozzle.

FIG. 2 is a diagram indicating a drain current I_(ds)-gate voltage V_(gs) characteristic that shows a device characteristic of a FET manufactured through the lithography process. Note that, in FIG. 2, a dashed line indicates an I_(ds)-V_(gs) characteristic of the conventional FET manufactured by removing remaining organic substances using the O₂ plasma ashing and a solid line indicates an I_(ds)-V_(gs) characteristic of the FET of the present invention manufactured by removing remaining organic substances using ozone water.

FIG. 2 shows that the FET of the present invention can obtain a better pinch-off characteristic compared to the conventional FET. This is because, in the conventional cleaning by the O₂ plasma ashing, the plasma damages the epitaxial layer 101 and leak components increase, while in the cleaning with ozone water in the present invention, the surface of the epitaxial layer 101 is not damaged since the plasma is not used.

FIG. 3 is a diagram indicating a result of comparing i) the number of particles of a FET manufactured without removing the remaining organic substances in the process shown in FIG. 1G, ii) the number of particles of a FET manufactured by removing the remaining organic substances by the O₂ plasma ashing, iii) the number of particles of a FET manufactured by removing the remaining organic substances with ozone water only, with iv) the number of particles of a FET manufactured by removing the remaining organic substances with ozone water and hydrogen water. Here, in FIG. 3, they are compared by converting the number of particles of the FET manufactured without removing the remaining organic substances into 1.

FIG. 3 shows that the removal of the remaining organic substances with the ozone water reduces the number of particles compared to the case where the remaining organic substances are not removed, and that the reduction rate is as much as that of the removal of the remaining organic substances by the O₂ plasma ashing. Moreover, the removal of the remaining organic substances with the ozone water and the hydrogen water reduces the number of particles compared to the case where the remaining organic substances are removed with the ozone water only. This is because that the oxidation of the ozone water is combined with the deoxidization of the hydrogen water so as to remove more remaining organic substances.

FIG. 4 is a diagram indicating an I_(ds) variation (δ I_(ds) in FIG. 4) of the FET in the case where the ozone concentration of the ozone water is changed in the process shown in FIG. 1G. That is, it is a diagram indicating an ozone concentration dependency of the I_(ds).

FIG. 4 shows that the I_(ds) variation gets larger when the ozone concentration gets higher than 13 mg/L. This is because that the oxidation on the surface of the epitaxial layer 101 progresses as the ozone concentration gets too high, the distance between the schottky electrode 111 and the i-type InGaAs channel layer 103 changes, and the I_(ds) changes accordingly. Therefore, according to the manufacturing method for the FET of the present invention, the ozone concentration is 13 mg/L or less so that the remaining organic substances can be removed without changing the I_(ds).

As described above, according to the lithography process of the FET in the present embodiment, the remaining organic substances are removed with the ozone water whose ozone concentration is 13 mg/L or less or whose pH is from 6 to 8 inclusive, the hydrogen water whose hydrogen ion concentration is from 6 to 8 inclusive. Therefore, the remaining organic substances can be removed without damaging the epitaxial layer so that the lithography process of the FET in the present embodiment can realize a lithography process of the FET that can remove the remaining organic substances without deteriorating the characteristic of the FET.

Also, according to the lithography process of the FET in the present embodiment, the cleaning is performed in a state where light is blocked to shade the epitaxial layer 101. Consequently, the epitaxial layer is not etched by a battery effect so that the lithography process of the FET in the present embodiment can realize the lithography process of the FET that can prevent further deterioration of the characteristic of the FET.

Additionally, according to the lithography process of the FET in the present embodiment, the cleaning is performed using both of the ozone water and the hydrogen water. Therefore, many of the remaining organic substances can be removed owing to the oxidation of the ozone water and the deoxidization of the hydrogen water. Further, the remaining fluid on the surface of the compound semiconductor layer can be removed by rinsing with hydrogen water so that the lithography process of the FET in the present embodiment can realize the lithography process of the FET that can clean the surface of the epitaxial layer more.

Here, in the lithography process of the FET in the present embodiment, the surface of the epitaxial layer 101 is cleaned after the schottky electrode 111 is formed. However, the surface of the epitaxial layer 101 can be cleaned, even after forming the ohmic electrode 109, with the ozone water whose ozone concentration is 13 mg/L or less or whose pH is from 6 to 8 inclusive, with the hydrogen water whose hydrogen ion concentration is from 6 to 8 inclusive, or with both of the ozone water and the hydrogen water. Consequently, the formation of oxides on the surface of the n-type GaAs ohmic contact layer 106 can be prevented so that the increase of a contact resistance is prevented and the deterioration of the characteristic of the FET is also prevented.

Further, in the present embodiment, the compound semiconductor device is considered as the FET. However, the compound semiconductor device does not limit to the FET, and other compound semiconductor devices may be used unless including a lithography process in the manufacturing process.

Moreover, in the present embodiment, the compound semiconductor device has a layer made of GaAs, AlGaAs and InGaAs. However, the compound semiconductor device may have a layer made of other compound semiconductor device materials, for example, such as InP or InGaP.

Additionally, in the present embodiment, the layer exposed for cleaning is the compound semiconductor layer made of AlGaAs or GaAs. However, the layer exposed for cleaning may be a compound semiconductor layer made of other compound semiconductor materials such as InGaAs, InGaP or InP.

Although only an exemplary embodiment of this invention has been described in detail above, those skilled in the art will readily appreciate that many modifications are possible in the exemplary embodiment without materially departing from the novel teachings and advantages of this invention. Accordingly, all such modifications are intended to be included within the scope of this invention.

INDUSTRIAL APPLICABILITY

The present invention can be used for a manufacturing method for a compound semiconductor device, in particular for a lithography process and the like in the manufacturing process for the compound semiconductor device. 

1. A manufacturing method for a compound semiconductor device comprising: a patterning process of forming a resist pattern on a compound semiconductor layer; and a removing process of removing said resist pattern and cleaning a surface of the compound semiconductor layer using at least one of ozone (O₃) water and hydrogen (H₂) water.
 2. The manufacturing method for the compound semiconductor device according to claim 1, wherein a concentration of the ozone water is 13 mg/L or less.
 3. The manufacturing method for the compound semiconductor device according to claim 2, wherein the cleaning of the compound semiconductor layer surface in the removing process is performed in a state where light is blocked.
 4. The manufacturing method for the compound semiconductor device according to claim 3, wherein in the removing process, the ozone water and the hydrogen water are used for the cleaning.
 5. The manufacturing method for the compound semiconductor device according to claim 4, wherein the compound semiconductor layer has a layer made of GaAs, AlGaAs, InGaAs, InGaP, or InP.
 6. The manufacturing method for the compound semiconductor device according to claim 5, wherein the compound semiconductor layer surface to be cleaned is made of GaAs, AlGaAs, InGaAs, InGaP, or InP.
 7. The manufacturing method for the compound semiconductor device according to claim 1, wherein a pH of the ozone water and a pH of the hydrogen water are from 6 to
 8. 8. The manufacturing method for the compound semiconductor device according to claim 7, wherein the cleaning of the compound semiconductor layer surface in the removing process is performed in a state where light is blocked.
 9. The manufacturing method for the compound semiconductor device according to claim 8, wherein in the removing process, the ozone water and the hydrogen water are used for the cleaning.
 10. The manufacturing method for the compound semiconductor device according to claim 9, wherein the compound semiconductor layer has a layer made of GaAs, AlGaAs, InGaAs, InGaP, or InP.
 11. The manufacturing method for-the compound semiconductor device according to claim 10, wherein the compound semiconductor layer surface to be cleaned is made of GaAs, AlGaAs, InGaAs, InGaP, or InP. 